#Gin Web Framework

Gin is a web framework written in Golang. It features a martini-like API with much better performance, up to 40 times faster. If you need performance and good productivity, you will love Gin.
Check out the official web site

Start using it

Run:

go get github.com/gin-gonic/gin

Then import it in your Golang code:

import "github.com/gin-gonic/gin"

##API Examples

Create most basic PING/PONG HTTP endpoint

import "github.com/gin-gonic/gin"

func main() {
    r := gin.Default()
    r.GET("/ping", func(c *gin.Context){
        c.String(200, "pong")
    })
    
    // Listen and server on 0.0.0.0:8080
    r.Run(":8080")
}

Using GET, POST, PUT, PATCH and DELETE

func main() {
    // Creates a gin router + logger and recovery (crash-free) middlewares
    r := gin.Default()
    
    r.GET("/someGet", getting)
    r.POST("/somePost", posting)
    r.PUT("/somePut", putting)
    r.DELETE("/someDelete", deleting)
    r.PATCH("/somePatch", patching)

    // Listen and server on 0.0.0.0:8080
    r.Run(":8080")
}

Parameters in path

func main() {
    r := gin.Default()
    
    r.GET("/user/:name", func(c *gin.Context) {
        name := c.Params.ByName("name")
        message := "Hello "+name
        c.String(200, message)
    })

    // Listen and server on 0.0.0.0:8080
    r.Run(":8080")
}

Grouping routes

func main() {
    r := gin.Default()
    
    // Simple group: v1
    v1 := r.Group("/v1")
    {
        v1.POST("/login", loginEndpoint)
        v1.POST("/submit", submitEndpoint)
        v1.POST("/read", readEndpoint)
    }
    
    // Simple group: v2
    v2 := r.Group("/v2")
    {
        v2.POST("/login", loginEndpoint)
        v2.POST("/submit", submitEndpoint)
        v2.POST("/read", readEndpoint)
    }

    // Listen and server on 0.0.0.0:8080
    r.Run(":8080")
}

Blank Gin without middlewares by default

Use

r := gin.New()

instead of

r := gin.Default()

Using middlewares

func main() {
    // Creates a router without any middleware by default
    r := gin.New()
    
    // Global middlewares
    r.Use(gin.Logger())
    r.Use(gin.Recovery())
    
    // Per route middlewares, you can add as many as you desire.
    r.GET("/benchmark", MyBenchLogger(), benchEndpoint)

    // Authorization group
    // authorized := r.Group("/", AuthRequired())
    // exactly the same than:
    authorized := r.Group("/")
    // per group middlewares! in this case we use the custom created
    // AuthRequired() middleware just in the "authorized" group.
    authorized.Use(AuthRequired())
    {
        authorized.POST("/login", loginEndpoint)
        authorized.POST("/submit", submitEndpoint)
        authorized.POST("/read", readEndpoint)
        
        // nested group
        testing := authorized.Group("testing")
        testing.GET("/analytics", analyticsEndpoint)
    }
   
    // Listen and server on 0.0.0.0:8080
    r.Run(":8080")
}

JSON parsing and validation

type LoginJSON struct {
    User     string `json:"user" binding:"required"`
    Password string `json:"password" binding:"required"`
}

func main() {
    r := gin.Default()
    
    r.POST("/login", func(c *gin.Context) {
        var json LoginJSON
        
        // If EnsureBody returns false, it will write automatically the error
        // in the HTTP stream and return a 400 error. If you want custom error 
        // handling you should use: c.ParseBody(interface{}) error
        if c.EnsureBody(&json) {
            if json.User=="manu" && json.Password=="123" {
                c.JSON(200, gin.H{"status": "you are logged in"})
            }else{
                c.JSON(401, gin.H{"status": "unauthorized"})
            }
        }
    })

    // Listen and server on 0.0.0.0:8080
    r.Run(":8080")
}

XML, and JSON rendering

func main() {
    r := gin.Default()
    
    // gin.H is a shortcup for map[string]interface{}
    r.GET("/someJSON", func(c *gin.Context) {
        c.JSON(200, gin.H{"message": "hey", "status": 200})
    })
    
    r.GET("/moreJSON", func(c *gin.Context) {
        // You also can use a struct
        var msg struct {
            Name string `json:"user"`
            Message string
            Number int
        }
        msg.Name = "Lena"
        msg.Message = "hey"
        msg.Number = 123
        // Note that msg.Name becomes "user" in the JSON
        // Will output  :   {"user": "Lena", "Message": "hey", "Number": 123}
        c.JSON(200, msg)
    })
    
    r.GET("/someXML", func(c *gin.Context) {
        c.XML(200, gin.H{"message": "hey", "status": 200})
    })

    // Listen and server on 0.0.0.0:8080
    r.Run(":8080")
}

####HTML rendering

Using LoadHTMLTemplates()

func main() {
    r := gin.Default()
    r.LoadHTMLTemplates("templates/*")
    r.GET("/index", func(c *gin.Context) {
        obj := gin.H{"title": "Main website"}
        c.HTML(200, "index.tmpl", obj)
    })

    // Listen and server on 0.0.0.0:8080
    r.Run(":8080")
}

You can also use your own html template render

import "html/template"
func main() {
    r := gin.Default()
    html := template.ParseFiles("file1", "file2")
    r.HTMLTemplates = html

    // Listen and server on 0.0.0.0:8080
    r.Run(":8080")
}

Custom Middlewares

func Logger() gin.HandlerFunc {
    return func(c *gin.Context) {
        t : time.Now()
        
        // Set example variable
        c.Set("example", "12345")
        
        // before request
        
        c.Next()
        
        // after request
        latency := time.Since(t)
        log.Print(latency)
    }
}

func main() {
    r := gin.New()
    r.Use(Logger())
    
    r.GET("/test", func(c *gin.Context){
        example := r.Get("example").(string)
        
        // it would print: "12345"
        log.Println(example)
    })

    // Listen and server on 0.0.0.0:8080
    r.Run(":8080")
}

Custom HTTP configuration

Use http.ListenAndServe() directly, like this:

func main() {
    router := gin.Default()
    http.ListenAndServe(":8080", router)
}

or

func main() {
    router := gin.Default()

    s := &http.Server{
	    Addr:           ":8080",
	    Handler:        router,
	    ReadTimeout:    10 * time.Second,
	    WriteTimeout:   10 * time.Second,
	    MaxHeaderBytes: 1 << 20,
    }
    s.ListenAndServe()
}